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• swresample/resample : speed up build_filter by 50%

  4 novembre 2015, par Ganesh Ajjanagadde

  swresample/resample : speed up build_filter by 50%
  This speeds up build_filter by 50%. This gain should be pretty
  
  consistent across all architectures and platforms.
  Essentially, this relies on a observation that the filters have some
  
  even/odd symmetry that may be exploited during the construction of the
  
  polyphase filter bank. In particular, phases (scaled to [0, 1]) in [0.5, 1] are
  
  easily derived from [0, 0.5] and expensive reevaluation of function
  
  points are unnecessary. This requires some rather annoying even/odd
  
  bookkeeping as can be seen from the patch.
  I vaguely recall from signal processing theory more general symmetries allowing even greater
  
  optimization of the construction. At a high level, "even functions"
  
  correspond to 2, and one can imagine variations. Nevertheless, for the sake
  
  of some generality and because of existing filters, this is all that is
  
  being exploited.
  Currently, this patch relies on phase_count being even or (trivially) 1,
  
  though this is not an inherent limitation to the approach. This
  
  assumption is safe as phase_count is 1 << phase_bits, and is hence a
  
  power of two. There is no way for user API to set it to a nontrivial odd
  
  number. This assumption has been placed as an assert in the code.
  To repeat, this assumes even symmetry of the filters, which is the most common
  
  way to get generalized linear phase anyway and is true of all currently
  
  supported filters.
  As a side note, accuracy should be identical or perhaps slightly better
  
  due to this "forcing" filter symmetries leading to a better phase
  
  characteristic. As before, I can’t test this claim easily, though it may
  
  be of interest.
  Patch tested with FATE.
  Sample benchmark (x86-64, Haswell, GNU/Linux) :
  test : swr-resample-dblp-44100-2626
  new :
  
  527376779 decicycles in build_filter(loop 1000),     256 runs,      0 skips
  
  524361765 decicycles in build_filter(loop 1000),     512 runs,      0 skips
  
  516552574 decicycles in build_filter(loop 1000),    1024 runs,      0 skips
  old :
  
  974178658 decicycles in build_filter(loop 1000),     256 runs,      0 skips
  
  972794408 decicycles in build_filter(loop 1000),     512 runs,      0 skips
  
  954350046 decicycles in build_filter(loop 1000),    1024 runs,      0 skips
  Note that lower level optimizations are entirely possible, I focussed on
  
  getting the high level semantics correct. In any case, this should
  
  provide a good foundation.
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] libswresample/resample.c

• Error recording an RTSP stream without transcoding

  23 août 2017, par Matt

  I’m trying to use FFmpeg to record RTSP streams from several security cameras. I have been successfully transcoding each stream for months now, but since this requires considerable CPU power, I’d like to simply copy each stream to disk in it’s original H.264 format.

  Whenever I try this, I receive and error similar to this (the "current" value varies) :

  Non-monotonous DTS in output stream 0:0 ; previous : 0, current : -62743 ;

  I’ve stripped most of the options I was using, although I really do want to keep -xerror so that FFmpeg quits when it encounters an error :

  ffmpeg.exe -xerror -i rtsp://admin:admin@192.168.1.135 -an -vcodec copy test.mp4

  And I still get this :

      ffmpeg version 3.3.3 Copyright (c) 2000-2017 the FFmpeg developers  
      built with gcc 7.1.0 (GCC)   
      configuration : —enable-gpl
      —enable-version3 —enable-cuda —enable-cuvid —enable-d3d11va —enable-dxva2 —enable-libmfx —enable-nvenc —enable-avisynth —enable-bzlib —enable-fontconfig —enable-frei0r —enable-gnutls —enable-iconv —enable-libass —enable-libbluray —enable-libbs2b —enable-libcaca —enable-libfreetype —enable-libgme —enable-libgsm —enable-libilbc —enable-libmodplug —enable-libmp3lame —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libopenh264 —enable-libopenjpeg —enable-libopus —enable-librtmp —enable-libsnappy —enable-libsoxr —enable-libspeex —enable-libtheora —enable-libtwolame —enable-libvidstab —enable-libvo-amrwbenc —enable-libvorbis —enable-libvpx —enable-libwavpack —enable-libwebp —enable-libx264 —enable-libx265 —enable-libxavs —enable-libxvid —enable-libzimg —enable-lzma —enable-zlib   
      libavutil      55. 58.100 / 55. 58.100   
      libavcodec     57. 89.100 / 57. 89.100   
      libavformat    57. 71.100 / 57. 71.100   
      libavdevice    57.  6.100 / 57.  6.100   
      libavfilter     6. 82.100 / 6. 82.100   
      libswscale      4.  6.100 / 4.  6.100  
      libswresample   2.  7.100 / 2.  7.100   
      libpostproc    54.  5.100 / 54.  5.100
      [udp @ 0000000002533b60] ’circular_buffer_size’ option was set but it is not supported on this build (pthread support is required) 
      [udp @ 0000000000ec97a0] ’circular_buffer_size’ option was set but it is not supported on this build (pthread support is required) 
      Input #0, rtsp, from ’rtsp ://admin:admin@192.168.1.135’ :   Metadata :
          title : RTSP Session/2.0   Duration : N/A, start : 0.837144, bitrate : N/A
          Stream #0:0 : Video : h264 (High), yuvj420p(pc, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 7 fps, 25 tbr, 90k tbn, 14 tbc Output
      #0, mp4, to ’test.mp4’ :   Metadata :
          title : RTSP Session/2.0
      y    encoder : Lavf57.71.100
          Stream #0:0 : Video : h264 (High) ([33][0][0][0] / 0x0021), yuvj420p(pc, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 7 fps, 25 tbr, 90k tbn, 90k tbc 
      Stream mapping :   Stream #0:0 -> #0:0 (copy) 
      Press [q] to stop, [?] for help
      [mp4 @ 00000000036b8340] Non-monotonous DTS in output stream 0:0 ; previous : 0, current : -62743 ; aborting.
      Conversion failed !
  

  Can anyone explain what the problem is and/or suggest the appropriate flags to handle this ?

• UVC webcam with ffplay outputs only noise ?

  1er mars 2024, par Abdulla Masud

  (My end goal is to use a UVC webcam with esp32 or raspberry pi. I was hoping to learn while doing some fun projects.)

  


  I have an old UVC webcam (Creative model ct6840) but I can't seem to get it to work with ffplay. I have tried looking through the documentation and other questions here but nothing is working for me. So far I have only been able to achieve a noisy-jittery output.

  


  Running ffplay -f rawvideo -video_size 670x480 /dev/video1, I get :

  


  

  


  Can someone help me understand how to make the camera work with ffplay ?

  


  The following is the information of my webcam :

  


  $ ffmpeg -f v4l2 -list_formats all -i /dev/video2

  


  [video4linux2,v4l2 @ 0x17eb3c0] Compressed: Unsupported :          GSPCA OV511 : 320x240 640x480


  


  $ v4l-info /dev/video2

  


  ### v4l2 device info [/dev/video2] ###
general info
    VIDIOC_QUERYCAP
    driver                  : "ov519"
    card                    : "USB Camera (05a9:0511)"
    bus_info                : "usb-0000:00:14.0-8.2"
    version                 : 6.1.79
    capabilities            : 0x85200001 [VIDEO_CAPTURE,?,READWRITE,STREAMING,(null)]

standards

inputs
    VIDIOC_ENUMINPUT(0)
    index                   : 0
    name                    : "ov519"
    type                    : CAMERA
    audioset                : 0
    tuner                   : 0
    std                     : 0x0 []
    status                  : 0x0 []

video capture
    VIDIOC_ENUM_FMT(0,VIDEO_CAPTURE)
    index                   : 0
    type                    : VIDEO_CAPTURE
    flags                   : 1
    description             : "GSPCA OV511"
    pixelformat             : 0x3131354f [O511]
    VIDIOC_G_FMT(VIDEO_CAPTURE)
    type                    : VIDEO_CAPTURE
    fmt.pix.width           : 640
    fmt.pix.height          : 480
    fmt.pix.pixelformat     : 0x3131354f [O511]
    fmt.pix.field           : NONE
    fmt.pix.bytesperline    : 640
    fmt.pix.sizeimage       : 614400
    fmt.pix.colorspace      : JPEG
    fmt.pix.priv            : 4276996862

controls
    VIDIOC_QUERYCTRL(BASE+0)
    id                      : 9963776
    type                    : INTEGER
    name                    : "Brightness"
    minimum                 : 0
    maximum                 : 255
    step                    : 1
    default_value           : 127
    flags                   : 48
    VIDIOC_QUERYCTRL(BASE+1)
    id                      : 9963777
    type                    : INTEGER
    name                    : "Contrast"
    minimum                 : 0
    maximum                 : 255
    step                    : 1
    default_value           : 127
    flags                   : 32
    VIDIOC_QUERYCTRL(BASE+2)
    id                      : 9963778
    type                    : INTEGER
    name                    : "Saturation"
    minimum                 : 0
    maximum                 : 255
    step                    : 1
    default_value           : 127
    flags                   : 32
    VIDIOC_QUERYCTRL(BASE+24)
    id                      : 9963800
    type                    : MENU
    name                    : "Power Line Frequency"
    minimum                 : 0
    maximum                 : 2
    step                    : 1
    default_value           : 0
    flags                   : 0
    VIDIOC_QUERYCTRL(BASE+32)
    id                      : 9963808
    type                    : BOOLEAN
    name                    : "Brightness, Automatic"
    minimum                 : 0
    maximum                 : 1
    step                    : 1
    default_value           : 1
    flags                   : 8


  


  Can someone guide me here please ? Any advice will be greatly appreciated 

  


  (P.S. the camera works perfectly with "guvcview" gtk application but since I want to use the camera with raspberry pi, I want it to work with ffplay...)